Pump structure



C. W: SHAW PUME STRUCTURE July 30, 1946.

2 Sheets-Sheet 1 Filed Dec. 2, 1942 9 me ATTORNEY July 30, 1946. c. w. SHAW 2,405,061

PUMP STRUCTURE v Filed Dec. 2, 1942 2 Sheets-Sheet 2 INVENTOR (Zara/70? W554 m A TTORNE Y5.

Patented July 30, 1946 PUMP STRUCTURE Clarence W. Shaw, Grosse Pointe Woods, Mich, assignor to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application December 2, 1942, Serial No. 467,565

Claims. 1

This invention relates to fluid pumps and par ticularly to pumps of the rotating positive displacement type, the principal object being the provision of a pump structure of this type of improved design and construction providing improved pumping characteristics.

Objects of the invention include the provision of a rotating pump of the positive displacement type capable of maintaining a predetermined pressure on the discharge side thereof within extremely close limits over a wide range of speeds; the provision of a pump of the type described particularly adapted for supplying fuel under pressure to internal combustion engines; the provision of a pump of the type described which is particularly efficient in passing volumes of gas therethrough which may become entrapped in the liquid being pumped thereby; and the provision of a pump of the type described in which the by passing of excess fluid between the discharge and intake side of the pump is accomplished ina simple, accurate and efficient manner.

Other objects of the invention include the provision of a rotating positive displacement type of pump including inner and outer gear-like elements rotating in a, surrounding casing and in which one side of the gear-like element is provided with a cooperating wall movable toward and from the same to provide for by-passing fluid between the inlet and outlet sides of the pump to maintain a predetermined pressure, the wall being mounted for movement axially on a rotating part whereby to eliminate the presence of static friction opposing this pressure controlling movement; the provision of a pump of the type described in which the discharge pressure of the pump acting on one face of the movable wall thereof is limited to a definite area of such wall and the suction pressure of the pump is applied to the entire opposite face thereof; the provision of a pump structure as above described in which the movable wall is formed for direct equalization between the suction pressure of the pump on one face thereof and the entire opposite face of the wall; the provision of a pump structure as above described in which the suction pressure of the pump is substantially atmospheric; and the provision of a pump structure of the type described in which the movable wall is provided with novel means for preventing its rotation upon its rotatable support.

Further objects of the present invention include the provision of a pump structure including internal and external inter-meshing gear-like pumping elements and a cooperating housing having end walls cooperating with the end faces thereof, one of the walls being movable toward and from the other thereof and said other of said end walls having inlet and outlet ports leading therethrough to said rotors or gear-like elements, and the outer of said gear-like elements is movable axially toward and away from the secondmentioned end wall in accordance with variations in pressure on the discharge side of said pump whereby to provide for direct by-pass of fluid between said inlet and said outlet without the necessity of passing through the gear-like elements; the provision of a pump structure as above described in which the outer gear-like element is normally urged towards engagement with the fixed wall of the housing through engagement with the movable wall thereof but in which it is freely movable axially between the fixed wall and the movable wall whenever the movable wall is retracted under the force of the discharge pressure of the pump; and the provision of a pump structure of the type described in which the bypassing of fluid between the inlet and outlet sides of the pump for the purposes of controlling the discharge pressure is accomplished in an easy and efficient manner.

Still further objects of the present invention is the provision of a pump structure as above described in which a filter or strainer is incorporated in the pump in a simple and efficient manner; and the provision of a pump structure as above described in which a filter or strainer of relatively large surface area is incorporated within the pump.

The above being among the objects of the present invention, the same consists in certain novel features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate suitable embodiments of the present invention and in which like numerals refer to like parts throughout the several different views,

Fig, 1 is a vertical sectional view taken axially through a pump structure embodying certain features of the present invention;

Fig. 2 is a vertical sectional view taken transversely of the pump structure shown in Fig. 1 as on the line 22 thereof;

Fig. 3 is a vertical sectional view taken transversely of the pump structure shown in Fig. 1 as on the line 33 thereof;

Fig. 4 is a fragmentary, vertical sectional view 3 taken transversely of the pump structure shown in Fig. l as on the line 4-4 thereof;

Fig. 5 is a fragmentary, horizontal sectional view taken on the line 5-5 of Fig. 4 to better illustrate the means employed for preventing the movable end wall from rotating with its supporting shaft;

Fig. 6 is a fragmentary view of a, portion of the construction illustrated in Fig. l to show the position of the movable end wall and the outer rotor under actual pumping conditions;

Fig. 7 is a vertical sectional view taken axially through a modified form of pump structure;

Figs. 8 and 9 are vertical sectional views taken transversely of the pump structure shown in Fig. '7 as on the line 8-8 and 9-9, respectively, thereof;

Fig. 10 is a view similar to Fig. '7 but showing a modified form of construction;

Fig. 11 is a vertical sectional view taken transversely of the pump structure shown in Fig. 10 as on the line H-H thereof; and,

Fig. 12 is a fragmentary, vertical sectional view taken axially through a pump structure of the general type shown in the preceding views and illustrating a modified form of construction for preventing rotation of the movable wall with respect to its rotating support.

In the broader aspects the present invention is capable of use in connection with various types of rotatable pumps of the positive displacement type and where the language of the claims so permits they are to be interpreted in this broad sense. The invention is, however, particularly adapted for use in connection with those types of positive displacement rotary pumps that include inner and outer members having inter-engageable tooth-like elements. One such type of pump is illustrated in United States Patent No. 1,682,563, issued August 28, 1928 to Myron F. Hill on Internal rotors, and, accordingly, such type of pump structure is illustrated in the drawings by way of explanation. Accordingly, in each of the pumps shown in the drawings there is an inner rotor 29 and an outer rotor 22, each of these rotors having tooth-like projections 24 and 26, respectively, which teeth intermesh with one another, The inner roto is mounted eccentrically to but on an axis parallel with the axis of rotation of the outer rotor, this eccentricity being such that at one point in the circumference of the pumping chamber which lies in the plane including the axes of rotation of the rotors 20 and 22 the teeth of the rotors completely engage one another and a tooth of one substantially completely fills the space between the teeth of the other. The outer rotor has one more tooth 26 than the number of teeth 24 of the inner rotor, the arrangement and design of the rotors being such that the teeth 24 and 26 are at all times in substantial engagement with one another. Thus from the point of full engagement of the teeth with one another when there is substantially no space between them the teeth, during rotation of the rotors, first recede from one another and then approach one another during each revolution of the rotors to provide variable volume chambers through which the pumping effect is obtained.

In the construction illustrated in Figs. 1 to 6, inclusive, the housing for the pump comprises a main body portion 23 inthe form of a casting having a flat righthand face, and a cap member 3i) suitably mounted and piloted on the righthand end thereof as viewed in Fig. l. A shaft 32 is rotatably mounted centrally of the main body portion 28 in suitable bearings 33 carried thereby and projects into the chamber formed within the cap 32. The righthand face of the main body portion 28 is disposed perpendicular to the axis of rotation of the shaft 32 and the inner rotor 20 is mounted on the shaft 32 in substantial contact with the righthand face of the housing 28. Any suitable means such as a key 34 may be provided between the shaft 32 and the inner rotor 20 to constrain the two for equal rotation with each other. Preferably some means is provided to lock the inner rotor against outward movement on the shaft 22, and a snap ring 35 partially received in a complementary peripheral groove in the shaft 32 and abutting the righthand face of the rotor 2:3 is shown in Fig. 1 for this purpose. The cap member 36 receives therein a wear ring or bushing 36 in transverse alignment with the inner rotor 20 and within which the outer rotor 22 is rotatably received. As is evident from an inspection of Figs. 2 and 3 the ring at is eccentric to the axis of the shaft 32 so as to position the rotors 20 and 22 in the proper relation with respect to each other as indicated in Fig. 3.

The righthand face of the main body portion as best brought out in Fig. 2 is provided with an intake port 38 and an outlet port 40, these ports bein of segmental conformation and extending approximately circumferentially with respect to the axis of the shaft 32 in overlapping or encompassing relation to the space exposed at one end of the rotors 20 and 22 between the teeth thereof and each at one side of a plane including the axis of the shaft 32 and passing centrally through the point of full mesh of the rotors. They approach each other relatively closely at the point of full mesh where the teeth of the inner and outer rotors completely engage one another and are spaced from each other to a greater extent at their opposite ends where such teeth are spaced from each other by a maximum distance, The inlet port 38 leads into an intake passage 42 within the main body portion 28 from which an opening 44 leads to an exterior face of the main body portion 28. Such opening may be threaded for reception of an intake pipe or tube such as 45. The outlet port 40 is similarly connected to a discharge passage 48 which communicates with an opening 50 leading to an exterior face of the main body portion 28 and which may be threaded for reception of a discharge pipe or tube such as 52.

The shaft 32 projects to the right beyond the inner rotor 29 and rotatably mounted upon such projecting end and within the cap member 30 is a plate member 54 of an outside diameter substantially equal to the outside diameter of the outer rotor 22. The lefthand face of the plate member 54 is flat and is constantly urged toward the left into contacting relationship with respect to the corresponding faces of the inner and outer rotors 20 and 22, respectively, by means of a coil spring 56 which is maintained under compression between the plate member 54 and the end wall of the cap member 30. The actual pumping chamber is thus formed between the righthand end of the main body portion 28 and the movable plate member 54 within the wear ring 36, and the plate member 54 thus forms a movable wall for this pumping chamber which is capable of moving axially of the shaft 32 against the force of the spring 55 in response to variations of pressure in the pumping chamber to maintain the discharge pressure substantially constant.

This general type of construction, that is one which employs a spring pressed plate to form a movable wall for one side of a pumping chamber is in itself broadly old, but in constructions as heretofore suggested I have found that it is impossible to accurately control the discharge pressure within the narrow limits required, for instance, in supplying fuel to internal combustion engines, for the reason that when the pump is driven at high speed the discharge pressure is built up beyond permissible limits. The construction shown involves certain departures from the prior. art along this general line through the medium of which the discharge pressures may be maintained within the required tolerances regardless of the speed of the pump and these will now be discussed. One reason why the pressures in the prior art pumps of this general type cannot be accurately controlled is that the movable wall was conventionally supported on fixed pins or the like between which and the movable wall static friction necessarily existed. In order to overcome this static friction in order to ad just itself to variations in pressure of the discharge side of the pump in an attempt to maintain a constant pressure the movable wall necessarily was required to overcome the static friction between it and its guiding means. The result was that when the speed of the pump increased and the volume pumped therefor increased, the discharge pressure was required to build up to an undesirable degree before it could overcome such static friction and cause the movable wall to properly respond in accordance therewith. Likewise when the speed of the pump was decreased and the volume pumped thereby correspondingly decreased the discharge pressure would drop below a desired minimum figure before the forces acting on the movable wall could overcome the static friction and allow the movable wall to move to accommodate such change in volume.

In the present case, the movable wall in being mounted upon the shaft 32 is mounted upon a rotating part so that no static friction exists between it and the shaft. Thus the static friction which caused the trouble in conventional constructions is eliminated in this construction in this respect. The only static friction necessary to be overcome .in the pump shown in Figs. 1 to 6, inclusive, is that in the connection between the movable wall 54 and the cap 30 for maintaining the movable wail against relative rotation with respect to the housing. This means, as illustrated best in Figs. 4 and 5, consists of a pin 58 secured in the movable wall or plate member 54 in parallel relation with respect to the axis of the shaft 32 and projecting to the right therefrom as viewed in Fig. 5. The cap member 30 is provided with a hollow boss 60 within which the pin 58 is axially loosely slidably received. It will be appreciated that, of course, the amount of static friction which is required to be overcome to eifect movement of the pin 58 within the hollow boss 60 is extremely small and offers no material resistance to axial movement of the movable wall for plate member 54 in response to changes in pressure acting upon the same. It will be noted that the periphery of the movable wall or plate member 54 is spaced from the inner walls of cap member 30 so that no static resistance can be set up at this point which would interfere with the free axial movement of the plate member 54.

Another reason why rotor pumps of the prior art employing a spring pressed end wall were not able to accurately control the discharge pressure of the pumps over a relatively wide range of speeds is that in all prior constructions that I am aware of the discharge pressure of the pump acted over substantially one-half the area of the movable wall and the suction pressure acted over the remaining half thereof, the tendency of the two pressures thus being to cook the plate relative to its guiding means thereby increasing the static friction which it was necessary to overcome before movement of the plate or movable end wall could occur in response to pressures existing in the discharge side of the pump. In accordance with the present invention such plate or movable end wall is either cut away or apertured on the suction side of the pumping element or elements so as to transmit the suction pressure on the pump to the back face of the movable plate or end wall. This feature, therefore, effects an equalization of the suction pressure acting on the operative face of the movable end wall with the pressure existing behind it and thus eliminates any pressure differential between the two opposite sides of the plate or movable end wall over that area thereof subject to the suction pressure of the pump and on the operative face thereof.

In the construction illustrated in Figs. 1 to 6, inclusive, the end wall 54 is provided with a slot 62 for the above described purposes, the slot 62 opening onto the adjacent marginal faces of the inner and outer rotors 20 and 22, respectively, at that point in the position of rotation thereof which is subjected to the suction pressures existing in the pump, Thus it will be appreciated that all of the space within the cap 30 back of the plate 5-5, or to the right thereof as viewed in Fig. 1, is subjected to the suction pressure of the pump and, therefore, the entire rear face of the plate member or movable wall 54 is subject to such suction pressure. In this connection it wili be readily appreciated by those skilled in the art that in many cases and perhaps the most cases, depending upon the position of the supply point from which the pump draws its liquid to be pumped, the pressure acting on the rear face of the plate 54 will be atmospheric pressure or substantially such pressure. In any event the pressure which exists on the back face of the movable wall of plate member 54 will remain substantially con-- 'stant throughout the entire operation of the pu'itip. As a result of the above described construction the only force effective on the operative face of the plate member or movable wall 54 is the discharge pressure of the pump and this is aided by the suction pressure of the pump which exists on an equivalent area from the back face thereof, in opposition to the force of the spring 56.

With the above described construction and unless compensated for, the center of pressure acting on the plate or movable Wall member 54 would still be concentrated on the plate or movable end wall member 54 on one side of the axis of the shaft 32 and would still have a tendency to cause the plate or movable end wall 54 to become cooked on the shaft. This possible disadvantage is overcome in accordance with a further phase of the present invention. According to this later-mentioned phase the spring 56 is so located with respect to the plate or movable end wall member 54 that it acts centrally of the center of pressure of the discharge side of the pump on the plate or movable end wall 54. In other words and as best brought out in Fig. 1 the spring 56 is not concentric with the shaft 32 but is arranged with its axis radially offset from the axis of the shaft 32 toward the discharge side of the pump, the amount of offset being such that the center of pressure of the spring 56 and the center of pressure of the discharge side of the pump on the plate member 54 are substantially coincident with one another. To maintain the spring 56 in such position the plate 54 is provided on its back face with an outstanding boss portion 54, best brought out in Fig. 4, which is disposed at the desired eccentricity and direction of offset with respect to the axis of the shaft 32 for the spring 56. The closed end wall portion of the cup-shaped cover 35, is likewise offset from the axis of the shaft 32 so that the spring 56 in seating against the end wall thereof will be arranged at the desired eccentricity with respect to the axis of the shaft 32. Thus the pressure of the spring 56 and the discharge pressure of the pump on the opposite face of the plate member 54 are balanced so as to eliminate any cocking tendency of the plate member 54 of the shaft 32. The result is that the plate member 54 is freely movable on the shaft 32 and being substantially free of any static friction in its axial movement is free to move in response to extremely slight variations of pressure on the discharge side of the pump to maintain such pressure constant. The sensitivity of the plate member 54 to changes in pressure on the discharge side of the pump is, of course, increased if the plate member 54 is constructed from a light metal such as aluminum or magnesium or suitable alloys thereof. This is preferably done. In such case the plate member 54 has less inertia to be overcome in effecting movement thereof than where constructed of a heavier metal as will be appreciated by those skilled in the art.

It will be noted from an inspection of Figs. 1 and 6 that the inside diameter of the wear ring or bushing 35 is less than the inside diameter of the cap member 30 immediately to the right thereof. Accordingly, it is possible for the outer rotor 22 to move to the right with the plate member 54 as the latter recedes under increased pressure within the pump chamber and this actually and desirably occurs as indicated in Fig. 6 which illustrates the plate member in receded position. This movement of the outer rotor 22 may be caused by the fact that its right-hand face being in flat contacting relation with respect to the operative face of the plate member 54 is sealed against the flow of liquid under the discharge pressure in the pump between them, while its lefthand face is at least partially exposed to the discharge pressure of the pump in the discharge port 4-0. Whatever the reason, the outer rotor 22 does follow the movement of the plate 54 in the latters movement toward or from the opposed face of the inner rotor 20, in response to variations in the discharge pressure of the pump.

The fact that the outer rotor 22 follows the movement of the plate 54 is important for the following reasons. If this movement did not occur, then as the plate member 54 receded from the rotors under an increased pressure and in order to permit a larger volume of liquid to be bypassed between the inlet and outlet sides of the rotors in an attempt to maintain a constant discharge pressure, it would require the by-passed liquid to flow axially through the length of the pump before it could be by-passed to the opposite side of the rotors. This flow of the liquid axially through the length of the pump under such circumstances is not required where the outer rotor follows the movement of the plate member 54 in accordance with the present invention as in such case as soon as the outer rotor moves away from the cooperating face of the main body portion 28,

a direct passage is provided between the outer rotor and the main body portion 28 between the inlet port 38 and the outlet port 40 around the exterior of the inner rotor 20 through which the liquid may flow or by-pass to maintain a constant discharge pressure. This feature is very important inasmuch as in the prior types of pumps where the outer rotor is not capable of following the movement of the plate member and where, for instance, the pump is intended to maintain a constant pressure of five pounds per square inch gage, as the speed of rotation of the pump is increased the pressure increases up to as much as fifteen pounds per square inch solely because of the resistance to flow of the liquid between the two pumping elements. With the present construction and because such Icy-passed liquid is not forced to flow through the pumping elements but is provided with a free and direct path of flow between the inlet and outlet sides of the pump, it has been found that the discharge pressure of the pump may be maintained extremely close to the desired maximum pressure for which the pump is adjusted even under those conditions where pumps designed according to the prior art as above described build up two or three times the desired pressure.

The above described pump may, of course, be mounted and driven in any suitable manner. In the particular construction shown the lefthand end of the main body portion 28 is provided with a flat face 10 arranged perpendicularly with respect to the axis of the shaft 32 and is centrally provided with an annular pilot portion 12. Accordingly, this pump is adapted to be received upon a fiat face provided upon the crankcase or other tructural part of an internal combustion engine with the pilot portion T2 closely fitting an opening provided therein for properly locating it on such face. The shaft 32 may, of course, be connected in any suitable manner to a rotating part of such engine but in the particular construction shown the lefthand end of the shaft 32 is hollow and its outer end portion is interiorly provided with axially parallel serrations 14. A stub shaft 76 provided exteriorly with axially parallel serrations 78 has one end thereof received within the end of the shaft 32 with the serrations 18 thereof interfitting with the serrations 74 of the shaft 32. To maintain the stub shaft 16 against axial movement with respect to the shaft 32 a snap ring 80 is partially received within a groove formed circumferentially of the stub shaft 16 in the outer portions of the serrations 18 thereof and abuts against the outer end of the shaft 32. A similar Snap ring 82 partially received within a groove formed at the righthand or inner end of the stub shaft 16 bears against the inner ends of the serrations 14 of the shaft 32 to lock the stub shaft 15 against outward movement with respect to the shaft 32'. A suitable hollow drive shaft (not shown) having internal serrations corresponding to the serrations '14 of the shaft 32 may envelope the outer end of the stub shaft it so that the driving force may be transmitted therefrom to the stub shaft 16 and from the stub shaft 16 to the shaft 32. The fit between the serrations 14 and 18 and also preferably between the serrations 18 and those of the driving shaft above explained but not shown, is sufficiently loose to permit a limited amount of universal movement of the stub shaft 16 in the shaft 32 and also in the drive shaft so as to eliminate the necessity of aligning the shaft 32 with the drive shaft with absolute accuracy.

In order to prevent the possibility of fuel escaping along the shaft 32 and into the crankcase or other part of the internal combustion engine where the pump is mounted directly upon the same, the lefthand face of the main body portion 28 is provided with a recess 84 around the corresponding end of the shaft 32 and within which a sealing device 85 is pressed. The recess 04 is provided with a smaller extension inwardly of the sealing device 85 forming a pocket 86 between the outer bearing 33 and the sealing device and this pocket is connected by a passage 81 with the suction passage 42 so a to permit a small amount of the pumped liquid to circulate over the bearing 33 for lubrication and any liquid that is pumped between the shaft 32 and the outer bearing 33 will be drawn back into the pump, thus preventing any liquid from finding its way along the shaft 32 into the engine.

It will be appreciated from the foregoing description and explanation that in accordance with the present invention certain improvements have been incorporated in a pump of the general type described which overcomes disadvantages in similar pump constructed in accordance with the prior art and that as a result of such improvements a pump having improved operating characteristics is provided.

In the construction illustrated in Figs. '7, 8, and 9 the main body portion 28a and the cap member 30a correspond with the main body portion and cap member of the previously described construction. Likewise the shaft 32a and the inner and outer rotors 20a and 22a, respectively, correspond with the shaft 32 and inner and outer rotors and 22 of the previously described construction. The cap member 30a in this case instead of terminating at its transverse 0r end wall as in the first construction has its side walls extended therebeyond and the outer ends of the same are closed by a sheet metal cap 90 which is secured to the cap member 30a by means of a screw 02 threaded into an outwardly projecting boss 04 formed on the transverse wall of the cap member 30a. An inlet passage 96 is provided through such side wall extension and is internally threaded for reception of an intake pipe or tube 98. The sheet metal cap 90 is provided with an inwardly projecting central boss portion I00 and the boss 94 is enlarged near its base and between these two portions a cylindrical screen I02 is mounted, the ends having a close fit with such portions. A passage I04 is provided through the transverse wall of the cap member 30a from the space within the screen I02 so that the liquid flowing through the inlet passage 95 must flow through the screen I02 before it may flow through the passage I04 to the space within the cap member 30a to the right of the rotors 20a and 22a. The screen I02 is of such fineness as to filter out foreign particles of objectionable size from the fluid being pumped.

Between the rotors 20a and 22a and the transverse wall of the cap member 30a a plate member 54a, corresponding to the plate member 54 in the previously described construction, is provided, but in this case instead of providing an opening such as 62 in the previously described plate on the suction side thereof, the same side of the plate is-cut off as best illustrated at I116 in Fig. 9, this having the same effect as providing the opening or slot 62 in the previously described construction. Thespring 56a which corresponds with the spring 56 previously described is arranged eccentrically with respect to the axis of the shaft 32a and collaborates with the plate 54a in substantially the same manner as the spring 56 cooperates with the plate 54 in the previously described construction. In the construction illustrated in Figs. '7, 8, and 9 no wear ring such as the wear ring 36 in the previously described construction is provided but instead the outer rotor 22a has bearing directly in the cap member 30a and is capable of moving axially therein with the plate member'54a in the same general manner as the equivalent parts in the previously described construction.

It will be appreciated that in the construction illustrated in Figs. '7, 8, and 9 the liquid flowing into the pump is admitted to one side of the rotors 20a and 22a while the main body portion is provided with a discharge port Ma on the opposite side of the rotors, the port 40a being connected to a discharge passage 48a which leads to the exterior face of the main body portion 28a in the same general manner as the discharge passage 48 in the previously described construction. Accordingly, the liquid being uinped must flow axially through the full width" f the rotors in passing through the pump and, unless otherwise taken care of, the advantages described in connection with the first described structure in being able to by-pass liquid between the intake and discharge sides of the pump without flowing through the rotors would not be realized. To obtain this same advantage the main body portion 20a is provided with a port 38a of substantially the same shape and contour as the inlet port 38 of the previously described construction but, of course,

': in this case such inlet port does not lead to the exterior face of the housing 28a. The only function of the port 38a is when the outer rotor 22a moves axially with the plate member 54a away from the coacting face of the main body portion 28a upon increase in volume ofthe liquid being pumped, liquid may be by-passed directly between the passage 38a and the discharge port 40a in exactly the same manner as in the previously described construction and without necessitating such liquid flowing through the length of the rotors. The only volume of liquid that will flow axially through the length of the rotors will be that actually discharged from the pump. Thus with the construction illustrated in Figs. '7, 8, and 9 the same lay-passing effect as in the previously described construction is obtained.

In the construction illustrated in Figs. '7, 8, and 9 the outer end of the shaft 32a is sealed against leakage of the fluid being pumped by means of a conventional type of seal Ill] and a drainage passage IIZ which connects the bearing for the shaft 32a in the main body portion .280. with the passage 38a which is, of course, under the suction pressure of the pump and which, therefore, serves the same purpose as the passage 87 in the first described construction.

It may also be noted that in the construction illustrated in Figs. '7, 8, and 9 the inner end of the shaft 32a is reduced in diameter and that the plate member 54a is rotatably mounted upon this reduced diameter portion. Also, that the transverse wall of the cap member 39a is provided with a central pocket in which a bushing II4, for the inner end of the shaft 32a is received. The bushing H4, therefore, provides an outboard bearing for the shaft 32a. It may also be noted that instead of the pin and boss construction employed in the first described construction for maintaining the plate member 540. against rotation, in the construction illustrated in Figs. '7, 8, and 9 the plate member 54a, as best brought out in Fig. 9, is provided with an integral radially projecting projection or boss H6 on its periphery which is loosely received within the groove or notch H8 formed in the inner wall of the cap member 30a, this construction simply providing an alternative method of maintaining the plate member 54a against rotation with the shaft 32a.

In the construction illustrated in Figs. 10 and 11 the same main body portion 28a is employed as in the construction illustrated in Figs. '7, 8, and 9. The cap member 301) is different, however, the extended side wall portions of the construction illustrated in Figs. 7, 8, and 9 being eliminated as well as the filter screen and sheet metal cap employed in the previous construction. In this case the cap is provided with an inlet passage I20, threaded to receive an inlet pipe I22, which discharges directly into the space between the righthand end of the rotors a and 2211. respectively, which are the same as in the previously described construction, and the end wall of the cap member 301). The plate member 5413 and spring 56b are substantially the same as the plate member 54a and the spring 56a in the previously described construction. In this case the shaft 32b, corresponding with the shafts 32 and 32a of the previously described constructions, is provided with an enlarged inner end I24 upon which the plate member 54b is rotatably received and the extreme free end portion of which is rotatably received in a bushing I26 carried by the transverse end wall of the cap member 30b. The plate member 541) in this case is cut away on its suction side in the same manner as in the construction of the plate member shown in Figs. '7, 81, and 9 but in this case instead of being held against rotation in the same manner as in such previously described construction, the plate member 54b is provided with a notch I30 in its periphcry and the cap member 30b is provided with an integral inwardly projecting rib or boss I32 which is received therein. Otherwise the construction illustratedin Figs. 10 and 11 is the same as that illustrated in Figs. '7, 8, and 9 and functions in the same manner. 7

In Fig. 12 a modified form of construction for maintaining the plate or movable end wall member against rotation with respect to the enclosing cap member is illustrated. The shaft in this case is illustrated at the outer rotor at 220, the inner rotor at 200, the movable end wall of plate member at 54c, and its cooperating spring at 56c, and all of which parts correspond with the equivalently numbered parts of the previously described constructions and which function in the same general manner. In this case, however, the plate member 540 is provided with an integral axially parallel pin portion I 40 cast integrally therewith and projecting to the right therefrom as viewed in Fig. 12. The cap member 300 is provided with a hollow boss I42 in which the projection I40 is loosely received thus to maintain the plate member 540 against rotation with the shaft 326.

Having thus described my invention, what I claim by Letters Patent is:

1. In a rotary pump, in combination, a housing having a substantially flat face therein, a shaft rotatably mounted in said housing in perpendicular relation with respect to said face and projecting therebeyond, a pair of rotors within said housing arranged with one end face of each thereof in opposed and parallel relation with respect to said face of said housing and one of said rotors being drive by said shaft, a wall within said,

320, the cap member at 30c,

housing movable axially with respect to said rotors and relatively rotatable with respect thereto, said wall having a flat face arranged in parallel and opposed relation with respect to the end faces of said rotors remote from said face of said housing, spring means constantly urging said movable wall toward said face of said housing, said face of said housing being provided with a pair of ports therein one registering with the suction side of said rotors and the other registering with the discharge side of said rotors forming the sole means for admitting and discharging fluid through said housing to and from the space within said rotor, the outer of said rotors being peripherally imperforate and bodily shiftable axially in said housing whereby said outer rotor may follow the movement of said movable wall in the movement of the latter toward. and from said face of said housing in response to variations in pressure on the discharge side of said pump structure, whereby to provide a by-pass passage of varying cross-sectional area between said outer rotor and said face of said housing between said ports and said movable wall being formed to provide constant open communication between the suction side of said pump and that face of said well remote from said rotors.

2. In a pump structure, in combination, a housing having a fiat face therein, a shaft rotatably mounted in said housing in perpendicular relationwith respect to said face, an inner rotor drivingly connected to said shaft within said housing i substantial contact with said face, an outer rotor within said housing surrounding said inner rotor in eccentric relation with respect thereto, a wall within said housing movable axially with respect to said rotors and relatively rotatable with respect thereto, said wall arranged in opposed relation with respect to those end faces of said rotors remote from said flat face of said housing, spring means constantly urging said movable wall toward said flat face of said housing, said fiat face of said housing having a pair of ports therein one of which is in communication with the inlet side of the pumping space between said rotors and the other of which is in communication with the discharge side of the pumping space between said rotors forming the sole means for admitting and discharging fluid through said housing to and from the space within said rotor, the outer of said rotors being peripherally imperforate and bodily movable Within said housing axially thereof under the influence of the discharge pressure acting on that end face thereof opposed to said flat face of said housing whereby to enable said outer rotor to follow the movement of said movable wall in response to variations in discharge pressure occurring in said pump, thereby providing a by-pass passage of varying cross-sectional size between said outer rotor and said flat face of said housing and extending between said ports, and said movable wall being formed to provide constant open communication between the suction side of said pump and that face of said wall remote from said rotors.

3. In a rotary pump, in combination, a housing having a flat face therein, a shaft rotatably mounted in said housing in perpendicular relationship with respect to said face, a peripherally imperforate inner rotor within said housing fixed for equal rotation with said shaft in concentric relation with respect thereto and said shaft projecting beyond one end of said rotor, a second peripherally imperforate rotor in said housing in enveloping and eccentric relation with respect to said inner rotor, said rotors providing cooperating pumping elements, said face of said housing having an inlet and an outlet port arranged in operative relation with respect to the suction and discharge sides of said rotors respectively and forming the sole means for the introduction and discharge of liquid to and from said rotors, a wall relatively rotatably and axially movably mounted on said projecting end of said shaft within said housing, means cooperating between said wall and housing preventing relative rotation between said wall and housing, said wall being formed to provide constant open communication between the suction side of said rotors and that face of said wall remote from said rotors, and spring means cooperating between said housing and wall constantly urging said wall towards said rotors, said spring means being arranged in eccentric relation with respect to the aXiS of said shaft and with the center of pressure thereof approximately in balancing relation with. respect to the discharge pressure of said pump acting on the opposite side of said wall.

4. In a rotary pump, in combination, a housing having a fiat face therein, a shaft rotatably mounted in said housing in perpendicular relationship with respect to said face, a peripherally imperforate inner rotor Within said housing fixed for equal rotation with said shaft in concentric relation with respect thereto and said shaft projecting beyond one end of said rotor, a second peripherally imperforate rotor in said housing in enveloping and eccentric relation with respect to said inner rotor, said rotors providing cooperaing pumping elements, said face of said housing having an inlet and an outlet port arranged in operative relation with respect to the suction and discharge sides of said rotors respectively and forming the sole means for the introduction and discharge of liquid to and from said rotors, a wall relatively rotatably and axially movably mounted on said projecting end of said shaft within said housing, means cooperating between said wall and housing preventing relative rotation between said wall and housing, and single spring means cooperating between said housing and wall constantly urging said wall towards said rotors, said spring means being arranged in eccentric relation with respect to the axis of said shaft and with the center of pressure thereof approximately in balancing relation with respect to the discharge pressure of said pump acting on 'he opposite side of said wall.

5. In a rotary pump, in combination, a housing having a fiat face therein, a shaft rotatably mounted in said housing in perpendicular relationship with respect to said face, a peripherally imperforate inner rotor within said housing fixed for equal rotation with said shaft in concentric relation with respect thereto and said shaft projecting beyond one end of said rotor, a second peripherally imperforate rotor in said housing in enveloping and eccentric relation with respect to said inner rotor, said rotors providing cooperating pumping elements, said face of said housing having an inlet and an outlet port arranged in operative relation with respect to the suction and discharge sides of said rotors respectively and forming the sole means for the introduction and discharge of liquid to and from said rotors, a wall relatively rotatably and axially movably mounted on said projecting end of said shaft within said housing, means cooperating between said wall and housing preventing relative rotation between said wall and housing, said wall being formed to provide constant open communication between the suction side of said rotors and that face of said wall remote from said rotors, and spring means cooperating between said housing and wall constantly urging said wall towards said rotors.

CLARENCE W. SHAW. 

